Standardization organizations such as 3GPP (3rd Generation Partnership Project) have studied and standardized public warning systems (PWS) serving as infrastructures for transmitting emergency information. The PWS is provided with functions of sending out warnings (warning notifications or alerts) to a plurality of mobile stations or user equipment (UE). Herein, the PWS can be classified into earthquake and tsunami warning systems (ETWS) and commercial mobile alert systems (CMAS).
Non-Patent Literature Document 1 discloses a sequence of sending out warnings with the CMAS. The sequence of sending out warnings with the CMAS will be described with reference to FIG. 17. First, a CBS (Cell Broadcast Service) 50 provides a CBC (Cell Broadcast Center) 40 with warning content, a broadcasting area, and a broadcasting period by use of an emergency broadcast request message (step S801). Based on the broadcasting area received from the CBS 50, the CBC 40 specifies a mobility management entity (MME) 30 configured to transmit a write-replace warning request. The CBC 40 provides the MME 30 with the warning content, the broadcasting area, and the broadcasting period by use of a write-replace warning request message (step S802). The MME 30 provides the CBC 40 with a write-replace warning response message indicating receipt of the warning content, the broadcasting area, and the broadcasting period (step 803).
Based on the broadcasting area received from the CBC 40, the MME 30 specifies a base station (i.e. eNode B) 20 configured to broadcast warnings. It provides the base station 20 with the warning content, the broadcasting area, and the broadcasting period by use of a write-replace warning request message (step S804). The base station 20 specifies a cell used to broadcast warnings based on the broadcasting area received from the MME 30. The base station 20 provides a mobile station 10, located in the cell, with the warning content by use of a system information block (SIB) of a broadcast control channel (BCCH) (step S805). Herein, the base station 20 broadcasts a plurality of warnings to the mobile station 10 in a time-division manner. The mobile station 10 receives a warning transmitted from the base station 20. Non-Patent Literature Document 2 discloses a technology of sending out a warning divided into a plurality of segments. Non-Patent Literature Document 3 defines a repetition period as a broadcasting period of warning being broadcast from the base station 20 to the mobile station 10, wherein it is set that the repetition period ranges from one second to 409 seconds.